Cellulose sponges and the washing machine

I wrote a post a few weeks back to complain about the sand coming to the surface in my terra cotta clay as I was throwing. I must say, I was frustrated.

But I did, as one person suggested and simply recycled it with some mother vinegar. I let it sit for two weeks.

Tonight I wedged it with some new terra cotta to be on the safe side. The clay threw relatively well. Not perfect but okay.

When I looked down tonight at my cellulose sponges (used for at least two years), I realized THIS may be the culprit of the sand.

You see, I like to wash my sponges with my aprons. I rinse everything thoroughly and then put all my throwing clothes and sponges into the machine with some mild detergent.

What I have noticed tonight was that my sponges are grainy. They are not nice and smooth the way they came out of the package. They are washing machine abused. What a realization??

To test my theory, I used only my hands and a red rib. Low and behold, the grain stayed down. I had no problems.

My guess is that these sponges work well with stone ware but leave heavy gouging in clay that should be smooth. I can only imagine if these sponges went on porcelain. It would be a mess.

Thus, tonight, I have decided that all the old sponges are going in the garbage. It is time. I have a new bag of sea sponges and two of those new blue ones people are using. I will stop being cheap and open the bag.

Has anyone else had this experience?? Is this an insight or is it my wishful thinking??

In my community studio, I never washed my sponges except under a tap. They lasted for years. Here, at home, I can wash them out. I think it is a bad move...really dumb move actually. This lesson absorbed at least a few hours in recycling and was making me dislike terra cotta when I usually love it.

So these are my insights for the night. Do not wash your sponges in the washing machine unless you are using them for something that does not require a smooth finish. They will break down.

Thank you to everyone who helped me with this issue and particularly the person who encouraged me to recycle that bunch of clay.

I use sea sponges, the Mudtool sponges (which are made of the same material surgical sponges are) and chamois . . . no cellulose sponges except for cleaning buckets, table tops, etc. It really doesn't matter how you wash the cellulose, they just are not good for clay surfaces . . . earthenware, stoneware or porcelain.

I use sea sponges, the Mudtool sponges (which are made of the same material surgical sponges are) and chamois . . . no cellulose sponges except for cleaning buckets, table tops, etc. It really doesn't matter how you wash the cellulose, they just are not good for clay surfaces . . . earthenware, stoneware or porcelain.

Dear Bciskepottery,

I have brand new one of each of these sponges. I have just been holding off using them. All those old ones are going straight into the trash. I have learned my lesson. It was the disintegration of the cellulose that was causing me problems. They seemed okay on my last bag of stone ware but they sure made a mess of the terracotta. Lesson learned.

Clay is made of particles of many sizes. When you sponge the clay (ANY sponge), the sponge removes the fine particles from the surface and exposes the larger particles. Use a metal or rubber rib if you want smooth surfaces.

I have to agree, a soft rubber rib is good for smoothing not a sponge. I will be looking into replacing some of my old sponges at NECEA.

see you there. If you see me, say hi. What will your name tag say?

Dear All,

I try to use both in the final stages of my throwing--rubber and a metal rib. But I was even having trouble even with the rib pulling up sand a few weeks ago. I am now convinced that it had to do with the disintegrating cellulose sponges digging into the clay.

Right now I have several boxes of terra cotta and some Arbuckle glaze waiting to go to spend the summer in majolica creation. Thus, a smooth, smooth surface before bisqueing is what I am after. I will burnish if that's what it takes.

I remember once hearing Walter Ostrom ask a class "what is the one thing you can never do enough of to clay?" We all looked at each other in wonderment and he said "compression." A smooth surface requires a compressed finish.

I recall seeing small pin holes coming through my pieces at the majolica glaze at his workshop. He pointed out that this was the direct effect of not compressing the clay in the final part of throwing and/or trimming. In short, it was not the glazes fault that I had pinholes on my pot but my lack of using a rib to compress the clay when finishing the piece.

Given my summer plans, I do not want kiln loads of pin holed pieces when a bit of simple smoothing of the surface would suffice in terms of my final detailing of the work.

Thank you all for the advice.

One day, one day in the next few years I will join you all at NCECA. I do envy you going on this trip. I am sure you will have a blast.